Prakas #796 On The First Amendment On The Prokas No.470_070809

PROKAS ON THE FIRST AMENDMENT ON THE PROKAS NO. 470, DATED JULY 16, 2004 ON THE ESTABLISHMENT OF ELECTRIC POWER TECHNICAL STANDARDS OF THE KINGDOM OF CAMBODIA

MINISTER OF INDUSTRY, MINES AND ENERGY

– Seen the Constitution of the Kingdom of Cambodia;
– Seen the Royal KRET No. NS/RKT/0704/124 Dated July 14, 2004 on the appointment of
the Royal Government;
– Seen the Royal KRAM No. NS/RKM/0196/05 Dated January 24, 1996 promulgating the
law on establishment of the Ministry of Industry, Mines and Energy;
– Seen the Royal KRAM No. NS/RKM/0201/ 03 Dated February 02, 2001 promulgating the
Electricity Law of the Kingdom of Cambodia;
– Seen the Prokas No. 470, dated July 16, 2004 on the establishment of Electric Power
Technical Standards of The Kingdom of Cambodia;
– Seen the urgent need and real situation at present;

DECIDES

Article 1
To amend the General Requirement of Electric Power Technical Standards of the Kingdom of
Cambodia issued by Prokas No. 470, dated July 16, 2004 as follow:

– To add the definition of the word “Remote Areas” at paragraph 19 of clause 1 (“Remote
Areas” means the areas whose electric demand is too small and whose grids are not
connected to other grids).
– To add paragraph 4 in clause 3 (4.Electrical Power Facilities in Remote Areas).
– To revise the table in paragraph 6.2 (Variation of Voltages) of clause 6 as follow:

Nominal System Voltage

Value to be Maintained

230V

Between 207 to 253V

400V

Between 360 to 440V

Nominal System Voltage Value to be Maintained
230V Between 207 to 253V
400V Between 360 to 440V
Article 2
Other conditions and contents of General Requirement of Electric Power Technical Standards of
the Kingdom of Cambodia issued by Prokas No. 470, dated July 16, 2004 besides the above
amendment shall remain unaltered and in force.

Article 3
Prokas or any decision in contradition to this Prokas shall be null and void.

Article 4
This Prokas shall come into force from the date of signing.

Minister of Industry Mines and Energy
Sign and Seal

SUY SEM

KINGDOM OF CAMBODIA

NATION RELIGION KING

GENERAL REQUIREMENTS OF ELECTRIC POWER TECHNICAL STANDARDS OF THE KINGDOM OF CAMBODIA

APRIL, 2004 ISSUED BY MINISTRY OF INDUSTRY, MINES AND ENERGY IN ACCORDANCE WITH THE ELECTRICITY LAW OF THE KINGDOM OF CAMBODIA

Clause 1: Definitions
In this General Requirements of Electric Power Technical Standards, unless the context
otherwise requires, the following terms shall have the meanings assigned against each term:
1. Dam
“Dam” means an artificial barrier across a stream including embankments, its foundations
and affiliated facilities such as spillways, constructed to store flowing water or divert it to
intakes for power generation.
2. Draw-in Conduit System
“Draw-in Conduit System” means an installation of underground lines, in which cables are
installed in conduits.
3. EAC
EAC is abbreviation of Electricity Authority of Cambodia.
4. Electrical Line
“Electrical Line” means the part of electric power facilities used to transmit or supply
electricity, which connects power stations, substations, switching stations and user’s sites,
and includes lines and associated protective devices and switchgears.
5. Electric Power Facility
“Electric Power Facility” means Generating Facilities, Substations, Switching Stations,
Electrical Lines, and dispatching centers, including equipment, buildings, dam, waterways,
fuel storageyards, ash disposal areas, etc.
6. Electrical Equipment
“Electrical Equipment” means electrically-charged facilities.
7. Generating Facilities
“Generating Facilities” means the electric power facilities used for generating electricity.
8. High-Voltage Line
“High-voltage Line” means an electrical line of voltage higher than 35kV
9. House Wiring
“House wiring” means the installation of user’s electrical equipment like wiring or devices
installed in houses or buildings etc for the purpose of using electricity. This installation
doesn’t include the installation of electrical equipments which are not user’s facilities, like
power generating facilities or substation installed in that place.
10. IEC
IEC is abbreviation of International Electrotechnical Commission
11. Indoor Electrical Appliances
“Indoor electrical appliances” means low-voltage incandescent lamps, discharge lamps, and
household and business electrical appliances installed indoors.
12. Insulated Conductor
“Insulated Conductor” means a cross-linked polyethylene (XLPE) insulated conductor for
the medium-voltage lines and XLPE insulated conductor or a polyvinyl chloride (PVC)
insulated conductor for the low-voltage line, according to the substance of the covering
insulator.
13. ISO
ISO is abbreviation of International Organization for Standardization .
14. Joint Use 7
“Joint Use” means a condition that electrical lines and/or communication lines belonging to
two or more owners are installed on the same supporting structure.
15. Licensee
“Licensee” means an electric power service provider who has been issued a license by the
EAC.
16. Low-Voltage Line
“Low-voltage Line” means an electrical line having voltage not more than 600V.
17. Medium-Voltage Line
“Medium-voltage Line” means an electrical line having voltage more than 600V but not
more than 35kV.
18. National Grid
“National Grid” means the high voltage backbone system of interconnected transmission
lines, substations and related facilities for the purpose of conveyance of bulk power.
19. Reservoir
“Reservoir” means stored water impounded by one or more dams or surrounding ground. It
also means land on which water is impounded to the highest water storage level.
20. RTU
RTU is abbreviation of “Remote Terminal unit” for SCADA system, installed at the electric
power facilities for monitoring the/fault status and control.
21. SCADA
SCADA is abbreviation of “Supervisory, control, and Data Aquisition” and means
equipment used for monitoring and receiving data.
22. Service Connection
“Service Connection” means an electrical link between a consumer’s site and Low-voltage
Line for supply electricity to that consumer.
23. Side by Side Use
“Side by Side Use” means a condition that electrical lines and/or communication lines of
one owner are installed on the same supporting structure.
24. Substation
“Substation” means electric power facilities to transform the voltage, including transformers,
lightning arresters, circuit breakers, disconnecting switches, potential devices, current
transformers, bus bars, protective relay systems for electrical lines and equipment and
devices, RTU for SCADA system, telecommunication facilities, etc.
25. Supporting Structure
“Supporting structure” means a structure to support electrical line, such as wooden poles,
iron poles, reinforced concrete poles and steel towers.
26. Switching Station
“Switching Station” means electric power facilities to change-over the electrical lines which
includes disconnecting switches, circuit breakers, bus-bars, protective relay system, RTU for
SCADA system, etc.
26. The Technical Standards
“The Technical Standards” means The Electric Power Technical Standards in the Kingdom
of Cambodia.
28. User’s Site
“User’s Site” means a place at which machines, apparatus and devices for using electricity
are installed.
29.Waterway
“Waterway” means a general term of channels and auxiliaries including gates and valves that
take flowing water, convey it to hydro-turbines, and discharge it into a river and so on for power
generation. “Waterway” is generally composed of intakes, forebays (settling basins), headraces, head
tanks or surge tanks, penstocks, tailraces, outlets, and other facilities.

PART 2 PURPOSE, AREA OF APPLICATION AND ENFORCEMENT

Clause 2: Purpose
This General Requirements of Technical Standards has the following main purposes:
1. To specify the technical, design, and operational criteria of Electrical Power Facility,
House Wiring and Electrical Appliance,
2. To ensure that the basic rules for supply of electricity are fair and non-discriminatory for
all Consumers of the same category, and
3. To maintain the technical standards (levels) of Electrical Power Facility, House Wiring
and Electrical Appliance installed in the Kingdom of Cambodia

Clause 3: Area of Application
All electrical power facilities, house wiring and electrical appliances, except the following
facilities, shall be in accordance with the Technical Standards.
1. Electrical equipment installed in airplanes, vessels, trains and vehicles
2. Electrical equipment operationg at voltage lower than 30V AC/DC which has not been
connected to the electric facilities of voltage 30V or more
3. Communication facilities other than the communication facilities for power system
operation

Clause 4: Enforcement
4.1 Jurisdiction
All persons who are related to electric power supply, electrical works, use of electricity,
manufacturing electric power facilities, trading in the facilities in the Kingdom of Cambodia
shall strictly follow the Technical Standards. The Technical Standards will not exempt any
concerned conditions stipulated in any other law or Regulations even though the matters not
stipulated in the Technical Standards.
4.2 Attention to be paid for Power Project
1. In planning of electric power projects, the feasibility studies shall be made to examine the
long term technical, economical and financial viabillity, and social acceptabillty.
2. The design, manufacturing, assembling and procurement of power facilities should be
such that the facilities can be operated with the designated performance for a long time. 9
Therefore, enough attention shall be paid in selection of the materials, safety factors, and
to easy operation, assembling/dismantling during operation and maintenance.
3. During installation of the electric power facilities and equipment and construction of the
facilities, enough attention shall be paid in selection of the materials and construction
management during the construction work.
4. In operation and maintenance of the electric power facilities, enough attention for
maintaining the required performance of the power facilities for long time and to protect
the environment in the surrounding areas, shall be paid.
5. In closing the electric power facilities, enough attention to the environmental and social
issues after closure of the facilities, shall be paid.
4.3 Licensees of power utilities shall employ qualified electrical engineers or technicians as
appropriated for supervision, operation and maintenance of the power facilities as provided
in the Technical Standards and other regulations.
4.4 Electrical works, such as house wiring, cable connection, installation of electrical equipment,
shall be carried out by qualified electricians. The works shall be carried out in accordance
with the Technical Standards.

Clause 5: Transitional Provision
1 The existing electric power facilities not harmful to human beings, animals and trees
could be operated till the time of its renewal or replacement.
2 The existing electrical power facilities harmful to human beings, animals and trees shall
be modified within two years to be satisfactory with the requirement of the Technical
Standards.

PART 3

QUALITY OF ELECTRIC POWER

Clause 6: Voltage

6.1 Standard Voltage
AC voltage shall be as follows below:

Classification
of voltage

Range of
Nominal Voltage

Nominal Voltage

Highest Voltage

Low
Voltage

600V or less

230/400V

Mediun
Voltage

More than 600V
35kV or less

22kV

24kV

High
Voltage

More than 35kV

115kV

123kV

230kV

245kV

If in the interest of development of the power sector in the Kingdom of Cambodia it becomes
necessary to use a nominal voltage other than that given in the table above, the Minitry of
Industry, Mines and Energy may allow the use of such nominal voltage as a standard voltage
through issuing Prokas.

6.2 Variation of voltages
The AC voltage at low voltage power supply points shall be maintained to the value
according to the nominal system voltage in accordance with the following table;

Nominal System Voltage

Value to be Maintained

230 V

Between 207 V and 244 V

400 V

Between 360 V and 424V

Clause 7: Frequency
The rating frequency is 50 Hz. The variation of the frequency shall be between 49.5Hz and
50.5Hz.
Clause 8: Continuity of Power Supply
1 Electric power supply shall be made continuously in accordance with the Regulations on
General Conditions of Supply of Electricity in the Kingdom of Cambodia issued by EAC.
2 In case of interruption in power supply, power system failure or loss of power, all electric
power licensees shall make all possible efforts to restore the normal conditions for continuous
power supply.

PART 4

PREVENTION OF ELECTRIC POWER DISASTERS

Clause 9: Prevention of Electric Power Disasters
The electrical equipment shall be installed in such manner as not to cause electrical shock, fire
and other accidents.
Clause 10: Prevention of Accidents Caused by Electric Power Facilities
The electric power facilities shall be installed with proper measures for operators not to touch
their moving parts, hot parts and other dangerous parts, and not to fall from them, accidentally.
Clause 11: Safety of Third Persons
1. Appropriate measures shall be taken to prevent third persons from entering into
compounds of power plants, substations and switching stations.
2. Appropriate measures shall be taken to prevent third persons from climbing supporting
structures of overhead electrical lines.
Clause 12: Prevention of Failures of Electric Power Facilities from Natural Disasters
Proper measures shall be taken for preventing failures of electric power facilities from
anticipated natural disasters such as floods, lightning, earthquakes, and strong winds.

PART 5

PREVENTION OF ELECTRIC POWER OUTAGE

Clause 13: Prevention of Electric Power Outage
1. When any generating facility is in serious fault, the generating facility shall be
disconnected from the power system so that the effect of the fault on the system can be
minimal and possibly the system could be operated, continuously.
2. When a power system fault occurs in system connected to generating facility, the
generating facility shall be disconnected from the system immediately, so that the
generator shall be continuously running with no-load to wait for the recovery of the
system from fault.
3. When a power system fault occurs affecting electrical lines, the power cut areas shall be
minimized as much as possible by disconnecting the faulty section or other suitable
methods.

PART 6

PRESERVATION OF ENVIRONMENT

Clause 14: Compliance with the Environmental Standards
To prevent the Environmental pollution, the electric power facilities shall be in accordance
with the environmental laws and regulations in the Kingdom of Cambodia.

CHAPTER 2

GENERAL REQUIREMENTS FOR ECTRIC POWER FACILITIES

PART 1GENERAL REQUIREMENTS FOR ALL FACILITIES

Clause 15:Applicable Standards

Electrical Power Facility, House Wiring and Electrical Appliance shall be as per the provision of the
Technical Standards. In case a matter is not stipulated in the Technical Standards, then IEC Standards
shall be applied. If it is not covered in IEC standards, then ISO Standards shall be applied. If it is not
covered in ISO Standards, then internationally recognized standards shall be applied subject to the
approval of EAC.

Clause 16:Life of Electrical Power Facility

1.Electrical power facilities shall be durable for a long time usage with efficient and stable operation.
2. Taking design of the electrical power facilities, selection of the materials, assembling and installation
of the equipment into consideration, suitable safety factors against foreseeable stresses, such as thermal
stress, mechanical stress, insulation strength, shall be considered.
3. To secure the power supply for a long time, necessary drawings, installation records, technical
manuals, instruction manuals, operation records necessary for the proper maintenance works on the
electrical equipment shall be provided.

Clause 17:Grounding
1.Grounding or other appropriate measures shall be provided for Electrical Equipment to prevent electric
shock, danger to human beings, fire, and other impediments to objects.

2.Grounding for Electrical Equipment shall be installed to ensure that current can safely and securely
flow to the ground.

Clause 18:Connection of Conductors

Conductors shall be connected as per following methods;
1. Conductors shall be connected firmly and the resistance of conductors shall not increase more than
resistance of conductors without connection.
2. Conductors shall be connected so that the insulating capacity of cables and insulated conductors shall
not decrease less than insulating capacity without connection.
3. The electrochemical corrosion shall not occur by connecting conductors of different kind of materials.

Clause 19:Communication System
To secure the power supply, necessary communication system shall be provided.

Clause 20: Accuracy of Power Meters
Power meters shall be accurate, fair and equitable power meters. The accuracy of Meter shall be
generally as follows:

1. Electro-magnetic mechanical power meter

Type of Customer

*Class

High-voltage customers

0.5

Medium-voltage customers

1.0

Low-voltage customers

2.0

*In accordance with IEC

2. Electronic power meter

Type of Customer

*Class

High-voltage customers

0.5

Medium-voltage customers

1.0

Low-voltage customers

2.0

*In accordance with IEC

PART 2

GENERAL REQUIREMENTS FOR THERMAL GENERATING FACILITIES

Clause 21: Boiler and its Accessories

21.1 Materials for Boiler and its Accessories
Vessels and tubes of the boiler, dependent superheater and steam storage vessel and its
accessories, the parts which are subject to an internal pressure higher than 0kg/cm2

(hereinafter, referred to as pressure parts) shall be made of materials having enough
mechanical strength and chemical stability under the maximum working pressure and
temperature.
21.2 Structure of Boiler and its Accessories
The pressure parts of the vessels and tubes of the boiler shall have enough safety margins
against the maximum stress under maximum working pressure or temperature condition. In
this case, the stress shall not exceed the allowable stress of the material.
21.3 Safety Valves
Vessels and tubes of the boiler which may be subjected to overpressure shall be equipped
with safety valve in order to release the pressure.
21.4 Feed Water System
1. The feed water system shall be able to avoid the thermal damage on the boiler during the
maximum evaporating condition.
2. In order to avoid the abnormal condition on the boiler feed water system, the boiler shall
be equipped with the standby feed water system.
21.5 Shutoff of Steam and Feed Water
1. The steam outlet of the boiler shall be able to be shutoff the steam.
2. The feed water inlet of the boiler shall be able to be shutoff automatically and firmly.
21.6 Drain Off Device For Boiler
In case of circulation boiler, the drain-off device shall be equipped which protect deposit
and to maintain the water level.
21.7 Monitor and Alarm System
Boiler and its accessories shall be equipped with the monitoring system to monitor the
running condition and the alarm system to protect from the damage of the boiler and its
accessories.

Clause 22: Steam Turbine and its Accessories

22.1 Materials for Steam Turbine and its Accessories
Cylinders, vessels and tubes of the steam turbine and its accessories and the pressure parts
shall be made of materials having enough mechanical strength and chemical stability under
the maximum working pressure and temperature.

22.2 Structure of Steam Turbine and Its Accessories
1. Structure of steam turbine shall have enough mechanical strength even when it is
operated at a speed, which the steam turbine reaches when the emergency governor is
actuated.
2. Structure of steam turbine shall have enough mechanical strength against the maximum
amplitude value of vibration produced on the major bearings and shaft.
3. Bearings of steam turbine shall have the construction to be able to support the load stably
during operation and without it’s abnormal wear and deformation, and overheat.
4. The critical speed of steam turbine and/or combined with generator or rotor on the same
shaft shall not be in the speed between the minimum speed of governor and the maximum
available speed of emergency governor. However, it will be exempted if it will be
arranged to have enough countermeasure against the vibration at critical speed during
operation of turbine.
5. The pressure parts and its accessories of the steam turbine shall have enough safety
margin against the maximum stress under maximum working pressure and temperature.
In this case, the stress shall not exceed the allowable stress of the material.

22.3 Governor
A steam turbine shall be equipped with a device to adjust automatically the steam entering
into the steam turbine in order to prevent its speed and output from fluctuating continuously
even in case of a change in load condition. The device to adjust the steam entering into the
steam turbine automatically shall have an ability to keep the turbine speed after the
interruption of the rated load below the speed at which the emergency governor is actuated.

22.4 Emergency Stop and Alarm Devices
1. A steam turbine shall be equipped with a device that functions to provide an alarm when
the amplitude value of vibrations was detected to be beyond the allowable level during
the turbine operation.
2. In order to avoid the occurrence of harm from overspeed or other abnormal conditions
during steam turbine operation, steam turbine shall be equipped with a device which
interrupts the inflow of steam automatically and a manual emergency stop device. When
the above emergency stop device is actuated, the emergency stop alarm shall be
energized.

22.5 Overpressure Protection Device
Steam turbine and its accessories which are likely to be subjected to overpressure shall be
equipped with an overpressure protection device in order to release the pressure.

22.6 Monitor and Alarm System
A steam turbine and its accessories shall be equipped with the necessary monitoring system to
monitor the operating condition and necessary alarm system to prevent any damages to the steam
turbine and its accessories during the operation.

Clause 23: Gas Turbine and its Accessories
16
23.1 Materials for Gas Turbine and its Accessories
Cylinders, vessels and tubes of the gas turbine and its accessories and the pressure parts
shall be made of materials which having enough mechanical strength and chemical stability
under maximum working pressure and temperature.
23.2 Structure of Gas Turbine and its Accessories
1. A gas turbine shall have enough mechanical strength for the structure even when it is
operated at a speed which the gas turbine reaches when the emergency governor is
actuated.
2. A gas turbine shall have enough mechanical strength for the structure against the
maximum amplitude value of vibration produced on the major bearings and shaft.
3. Bearings of gas turbine shall have the construction to be able to support the load stably
during operation and without it’s abnormal wear and deformation, and overheat.
4. The critical speed of gas turbine and/or combined with generator or rotor on the same
shaft shall not be in the speed between the minimum speed of governor and the maximum
available speed of emergency governor. However, it will be exempted if it will be
arranged to have enough countermeasure against the vibration at critical speed during
operation of turbine.
5. The pressure parts and its accessories of the gas turbine shall have enough safety margin
against the maximum stress under the maximum working pressure and temperature. In
this case, the stress shall not exceed the allowable stress of the material

23.3 Governor
A gas turbine shall be equipped with a device to adjust automatically the energy entering
into the gas turbine in order to prevent its speed and output from fluctuating continuously
even in case of a change in load condition. The device to adjust the energy entering into the
gas turbine automatically shall have an ability to keep the turbine speed after the
interruption of the rated load below the speed at which the emergency governor is actuated.

23.4 Emergency Stop and Alarm Device
1. A gas turbine shall be equipped with a device that functions to provide an alarm when the
amplitude value of vibrations was detected to be beyond the allowable level during the
gas turbine operation.
2. In order to avoid the occurrence of harm from overspeed or other abnormal conditions
during gas turbine operation, gas turbine shall be equipped with a device which interrupts
the inflow of gas automatically and a manual emergency stop device. When the above
emergency stop device is actuated, the emergency stop alarm shall be energized.

23.5 Overpressure Prevention Device
Gas turbine and its accessories which are likely to be subjected to overpressure shall be
equipped with an overpressure protection device in order to release the pressure.

23.6 Monitor and Alarm System
A gas turbine and its accessories shall be equipped with the necessary monitoring system to
monitor the operating condition and the necessary alarming system to prevent the damages
of gas turbine and its accessories during the operation.

24.1 Material for Internal Combustion Engine and its Accessories
Cylinders, vessels and tubes of the internal combustion engine and its accessories, the
pressure parts shall be made of the materials which have enough mechanical strength and
chemical stability under the maximum working pressure and temperature. 17

24.2 Structure of Internal Combustion Engine and its Accessories
1. An internal combustion engine shall have enough mechanical strength even when it is
operated at a speed which the internal combustion engine reaches when the emergency
governor is actuated.
2. Bearings of the engine shall have the structure to be able to support the load stably during
operation and without it’s abnormal wear and deformation, and overheat.
3 The pressure parts and its accessories which belong to the engine shall have enough
safety margins against the maximum stress under the maximum working pressure and
temperature. In this case, the stress shall not exceed the allowable stress of the material.

24.3 Governor
An engine shall be equipped with a device to adjust automatically the energy entering into
an engine in order to prevent its speed and output from fluctuating continuously even in case
of a change in load condition.
24.4 Emergency Stop Device
In order to avoid the occurrence of harm from overspeed or other abnormal conditions
during the engine operation, the engine shall be equipped with a device which interrupts the
inflow of fuel automatically and a manual emergency stop device. When the above
emergency stop device is actuated, the emergency stop alarm shall be energized.

24.5 Overpressure prevention Device
An engine and its accessories which are likely to be subjected to overpressure shall be
equipped with an overpressure protection device in order to release the pressure.

24.6 Monitoring and Alarming System
An engine shall be equipped with the necessary monitoring system to monitor the operating
condition and the necessary system to provide an alarm to prevent the damages of the
engine and its accessories during the operation.

Clause 25: Gas-Turbine Combined Cycle and its Accessories
Gas Turbine Combined Cycle and its Accessories shall be designed, manufactured,
constructed and operated in accordance with the above Clause 21, 22 and 23.

PART 3

GENERAL REQUIREMENTS FOR HYDRO POWER GENERATING FACILITIES

Clause 26: Dams, Waterways, Powerhouses and Other Facilities

26.1 Prevention of Overflow from Non-overflow Sections of Dams
Every dam shall be equipped on or near its body with a spillway capable of safe and secure
discharge of an inflow design flood, and every dam body shall have an adequate freeboard,
in order to prevent overflow of water from non-overflow sections of the dam for dam safety.

26.2 Dam Stability
1. Dam bodies shall be stable for sliding, overturning, and have required strength and
durability for dam stability. Fill dam bodies shall be stable for sliding, and have required
strength and durability for dam stability.
2. Dam foundations and the contact areas between the dam body and its foundations shall
be stable for sliding, and have the required strength for dam stability.

26.5 Prevention of Failure of Waterways
1. Waterways shall be structurally stable for anticipated loads, and not be damaged by
disasters such as a landslide and a flood.
2. Waterways shall be able to safely and securely discharge and control a design plant
discharge, and be hydraulically stable.
26.6 Prevention of Failure and Damage of Powerhouses and Other Facilities
Structures related to hydroelectric power civil engineering facilities such as powerhouses,
maintenance roads, and temporary facilities for construction works shall be stable for anticipated
loads, and not suffer failure and damage due to a landslide and a flood.

Clause 27: Prevention of Damage caused by Hydroelectric Power Plant

27.1 Prevention of Damage to Reservoirs and Ground around Reservoirs
1. Reservoirs shall not cause harmful water leakage to the surrounding ground, seepage
failure of the ground, and large-scale landslides.
2. Proper measures shall be taken if submergences of properties such as houses and
buildings may occur at upstream areas of a reservoir due to rises in water level caused by
the reservoir sedimentation.
19
27.2 Prevention of Damage to Downstream Areas of Dams and those of Outlets
1. Damage due to discharge from a dam to the downstream area under conditions of floods
shall not increase in comparison with the damage of no dam existence.
2. Proper measures shall be taken if damage to humans or properties, and impacts on the
surrounding environment and so on may occur at the downstream areas due to discharge
from dams.
3. Proper measures shall be taken if a rapid change in water level at downstream area of an
outlet due to discharge from a hydroelectric power plant may cause damage to the
downstream area.

28.5 Protective Devices for Hydraulic Turbines and Generators
Hydraulic turbines and generators shall be equipped with devices to disconnect the generators
from the electrical circuits and to stop the hydraulic turbines automatically in case any
abnormality that may cause significant damage and/or make serious trouble to the supply of
electricity occurs.

In General, the Technical Standards shall also applicable to renewable energy generating
facilities including photovoltaic generation, wind power, bio-mass or bio-gas generation,
portable generators and small hydropower generation including micro-hydro generation.
However, some of the conditions of the clauses stipulated in the Technical Standards which may
be difficult to be applied to such generating facilities because of special features of the facilities
and/or the circumstances. Relaxation from these conditions may be allowed on application from
the prospective owner with the reasons if it is judged reasonable.

Clause 30: Pumped Storage Generating Facilities
The Technical Standards shall be applicable to the generating facilities. Since the Technical
Standards are not enough for the generating facilities, an additional version of the Technical
Standards on the generating facilities will be issued and promulgated by the time when it is
needed.

PART 5

GENERAL REQUIREMENTS COMMON FOR TRANSMISSION AND DISTRIBUTION FACILITIES

Clause 31: Property of Conductors

1. The conductor of transmission and distribution facilities shall be cables, insulated
conductors or bare conductors. Bare conductors shall not be used for low-voltage lines.
2. Cables and insulated conductors shall have sufficient insulation capacity appropriate for
the conditions of the applied voltage.

Clause 32: Prevention of Climbing on Supporting Structures

As for supporting structures of electrical lines, following measures shall be taken to prevent
danger to third persons.

1. Any metal steps of supporting structures shall not be installed at the height of 1.8m or
less from the ground.
2. Warning signs to make third persons recognize danger shall be installed at each
supporting structure.
3. As for high-voltage lines, appropriate devices shall be installed at all legs of supporting
structures to prevent third persons from climbing the supporting structures. However, in
case that the supporting structures are located at places where third persons hardly
approach such as in the mountains or the supporting structures are surrounded by fences
or walls with appropriate height, this article shall not be applicable.

As for tensile strength of conductors and ground wires for overhead electrical lines except for
cables, the safety factor shall be not less than 2.5.

Clause 34: Side by Side Use and Joint Use of Electrical Lines or Communication Lines

34.1 High-Voltage Lines, Medium-Voltage Lines and Low-Voltage Lines
Side by side use and joint use of electrical lines shall be done by following methods.

1. When a high-voltage line and a medium-voltage line are installed at the same supporting
structure, the medium-voltage line shall be installed under the high-voltage line and on
separate cross arms.
2. When a medium-voltage line and a low-voltage line are installed at the same supporting
structure, the low-voltage line shall be installed under the medium-voltage line and on
separate cross arms.
3. No low-voltage line shall be installed at the same supporting structure where a high-
voltage line is installed.

34.2 Electrical Lines and Communication Lines
Side by side use and joint use of electrical lines and communication lines shall be done by
following methods. If communication lines are optical fibers and they are tied to electrical
lines or ground wires, this may not be applicable.
1. When a medium-voltage or a low-voltage line and a communication line are installed on
the same supporting structure, the medium-voltage or the low-voltage line shall be
installed above the communication line and on separate cross arms.
2. No communication line shall be installed at the same supporting structure where a high-
voltage line is installed.

Clause 35: Underground Lines

35.1 Cables shall be used for underground electrical lines.

35.2 In case that underground lines are installed with draw-in conduit system, tubes shall
withstand the pressure of vehicles and other heavy objects.

35.3 In case that underground lines are installed with a direct burial system, they shall be
installed in accordance with following methods.

1. Installation of proper plates above the underground lines or other proper measures shall
be taken to protect the underground lines against mechanical shocks.

2. The installed position of underground facilities shall be no less than 1.2 m in depth at a
place where there is a danger of receiving pressure from vehicles or other objects, and no
less than 0.6 m at other place.

Clause 36: Protection against Over-current

Protection equipment against over-current shall be installed at the appropriate places of
electrical circuits to prevent electrical equipment from over-heating due to excessive current and
not to cause fire.

Clause 37: Protection against Ground Faults

Protection equipment against ground faults or other appropriate measures shall be provided to
prevent damage of electrical equipment, electrical shock and fire.

Clause 38: SCADA System for Load Dispatching Center

1. RTU for SCADA System shall be installed in electric power facilities so that the state of
the National Grid could be monitored and control of the Power Facilities could be made
at the Dispatching Center.
2. Necessary telecommunication system shall be installed among Dispatching Center and
electric power facilities. As the redundancy, at least two different telecommunication
systems shall be required for the National Grid.
Clause 39: Classification of Grounding for Electrical Lines.

The types of grounding, the places to be applied, installation conditions, resistance value to
earth of distribution line shall be as given in the following table;

Kinds of groundings

Grounding type

Application

Installation conditions

Resistance to earth (Ω)

System
grounding

MV/LV
transformer

Low-voltage neutral
conductor of TT or TN
grounding type

Value prescribed for Class
B grounding work

Safety
grounding

Exposed
conductive
parts(*1)

For high-voltage lines(*2)

Value prescribed for Class
A grounding work

For medium-voltage

For low-voltage exceeding
300 V

Value prescribed for Class
C grounding work

For low-voltage not
exceeding 300 V

Value prescribed for Class
D grounding work

Arrester
grounding

Surge
arrester

For medium-voltage

Value prescribed for Class
A grounding work

Remarks

(*1) “Exposed conductive parts” refers to parts such as steel stands, metal case or the like of
apparatus installed in the electrical circuit.

(*2) Groundings for high-voltage substations and switching stations shall be individually
designed, depending on the short-circuit capacity.
Class A – Class D resistance value to earth shall be equal to or less than the value given in the
following table.

Classification of
grounding work

Resistance to
earth

Conditions for easement of resistance value

Class A

10Ω or less

Class B

10Ω or less
(When
1 * I
230
is
less than 10,
resistance to
earth shall be
the value of
1 * I
230
or less.)

In cases where voltage to earth of a low-voltage
electrical circuit exceeds 230V due to power contact
between the medium-voltage electrical circuit and
the low-voltage electrical circuit of the transformer,
when an earth leakage breaker that cuts off the
electrical circuit within 1 second is installed,
1 *
I
600
Ω
or less. When
1 * I
230
becomes less than 5Ω, it shall not

be necessary to obtain resistance less than 5Ω.

Class C

10Ω or less

In the case where grounding arises in a low-voltage
electrical circuit, when an earth leakage breaker that
acts within 0.5 seconds is installed, the resistance
value shall be 500Ω or less.

Class D

100Ω or less

In the case where grounding arises in a low-voltage
electrical circuit, when an earth leakage breaker that
acts within 0.5 seconds is installed, the resistance
value shall be 500Ω or less.

1. Supporting structures of overhead lines shall be designed, taking into account the following loads.

Kinds of Loads

Type of Load

Components of Load

Vertical loads

Weight of the supporting structure

Weight of the conductors and the ground wires and the accessories
supported by the supporting structure

Weight of the insulator strings and the fittings supported by the
supporting structure

A vertical component of the maximum tension of the guy wires
supporting the supporting structure, if any

Horizontal
transverse loads

Wind pressure of the supporting structure under the maximum wind
velocity

Wind pressure of the conductors and the ground wires supported by the supporting structure under the maximum wind velocity

Wind pressure of the insulator strings and the fittings supported by the
supporting structure

A horizontal transverse component of the maximum tension of the
conductors and the ground wires supported by the supporting structure
and the guy wires supporting the supporting structure, if any

Horizontal
longitudinal
loads

Wind pressure of the supporting structure under the maximum wind
velocity

A horizontal longitudinal component of the unbalanced maximum
tension of the conductors and the ground wires supported by the
supporting structure and the maximum tension of the guy wires
supporting the supporting structure, if any

2. Supporting structures and foundations of overhead high-voltage lines shall be designed in
consideration of the value of wind pressure based on the assumed maximum wind velocity in Cambodia.
3. Supporting structures and foundations of overhead high-voltage lines shall be designed so that those withstand the maximum loads, in consideration of appropriate safety factors.
4. In cases that overhead high-voltage lines are installed at places on the worst conditions such as inside river areas, windy areas, and so on, the supporting structures and the foundations shall be designed to withstand such the severe conditions.
Clause 41: Safety Factor of Fittings for Conductors and/or Ground Wires of Overhead
High-voltage Lines

Safety factor for the tensile strength (the maximum tensile strength, breaking strength) of
fittings of conductors and ground wires for overhead high-voltage lines shall be 2.5 or more.

The following measures shall be taken for overhead high-voltage lines to decrease the number
of electrical faults and to protect equipment from damage by the faults.

1. Installation of ground wires for overhead high-voltage lines
2. Installation of arcing horns for both ends of insulator assemblies of overhead high-voltage
lines
3. Installation of armor rods to wrap conductors by a clamp of suspension insulator
assemblies of overhead high-voltage lines

Clause 43: Bare Conductors of Overhead High-voltage Lines

1. Vibration Dampers
An appropriate type and number of dampers shall be installed to prevent fatigue of bare conductors and ground wires for overhead high-voltage lines due to their aeolian vibration.
2. Connection In case that bare conductors and ground wires are jointed with each other or with insulated conductors or cables, the connection shall conform to the following requirements in addition to the Clause 18.

(1) Bare conductors and ground wires shall be connected with compression type sleeves or compression type devices.
(2) Tensile strength of connection of bare conductors and ground wires shall be 95 % or more of the tensile strength of the connected bare conductors and ground wires.
However, this requirement shall not be applied to cases where the maximum tension to be designed is substantially smaller than the ultimate strength of the bare conductors and ground wires such as jumper conductors, the end span to substations and others.

1. Clearance among bare conductors and supporting structures, arms, guy wires and/or pole braces of overhead high-voltage lines shall be as follows. The clearances shall be secured, in any cases of the maximum swing of conductors under the maximum wind velocity to be designed, as follows;

Nominal Voltage

Clearance

115kV

No less than 0.70m

230kV

No less than 1.45m

2. Clearance among ground wires and the nearest conductor in the same span shall be larger
at any points in the span than the clearance of the supporting points at the both sides of
the span.

Clause 45: Height of Overhead High-voltage Lines

Height of conductors of overhead high-voltage lines shall be as follows.

1. Height in urban areas
Height of conductors of overhead high-voltage lines in urban areas shall be no less than the value by adding 0.06 m for every 10kV over 35kV to 6.5m,
2. Height in areas where third persons hardly approach Height of conductors of overhead high-voltage lines in areas where third persons hardly
approach shall be no less than the value by adding 0.06 m for every 10kV over 35kV to 5.5m.
3. Height over roads and/or railways Height of conductors of overhead high-voltage lines crossing over roads and/or railways shall be no less than the value by adding 0.06 m for every 10kV over 35kV to 13m.
4. Height over rivers and/or seas
Height of conductors of overhead high-voltage lines crossing rivers and/or seas shall be as follows.

At places with no vessel passage

At places with vessel passage

From the highest water level

From the highest point of vessels on the highest
water level(*1)

No less than the value by adding
0.06 m for every 10kV over 35kV
to 5.5m;

No less than the value by adding 0.06 m for every
10kV over 35kV to 3m;

(*1) The highest point of vessels shall be decided taking into account the future possibility.

5. All the heights described above shall be secured in any cases of the maximum sagging of
conductors in the maximum temperature to be designed.

Clause 46: Clearance among Overhead High-voltage Lines and Other Facilities or Trees

Clearance among each conductor of overhead high-voltage lines and other facilities or trees shall be as follows;
1. Clearance to other facilities
Clearance among each conductor of overhead high-voltage lines and other facilities shall
be no less than the value by adding 0.06 m for every 10kV over 35kV to 3m.
2. Clearance to trees
Clearance among each conductor of overhead high-voltage lines and trees shall be no less than the value by adding 0.06 m for every 10kV over 35kV to 2m.
3. The clearances described above shall be secured in any cases of the maximum sagging of conductors in the maximum temperature and/or the maximum swing of conductors under the maximum wind velocity to be designed. Clause 47: Prevention of Danger and Interference due to Electrostatic Induction and Electromagnetic Induction

1. The electrical field, which is caused by overhead high-voltage lines, at 1 m above the ground surface shall be 3kV/m or less, except for overhead high-voltage lines in the places where third persons seem to hardly approach such as in the mountains, in farming land and so on.
2. Conductive materials on the surface of the buildings under overhead high-voltage lines shall be grounded with the Class D in accordance with Clause 39.
47.2 Electromagnetic Induction

Surge arresters shall be installed at the appropriate places of Electrical Lines.

PART 7

TRANSMISSION AND DISTRIBUTION FACILITIES (MEDIUM AND LOW VOLTAGE)

Clause 49: Supporting Structures

49.1 Safety Factor of Foundation of Supporting Structures

1. The safety factor of foundation of supporting structure for low-voltage lines shall be 2 or more to the wind load.
2. The safety factor of foundation of supporting structure for medium-voltage lines shall be 2 or more to the load prescribed in Clause 40.
3. If wooden poles, iron-poles and iron-reinforced concrete poles are installed at other than soft ground in accordance with the following table, this clause may not be applicable.

Design Loadofsupportingstructure

Length of Poles

Setting depth

Span

Wooden
pole

15m or less

1/6 of
overall
length or
more

Medium-voltage lines in
urban area: No more than
75mOthers: No more than
150m.

50.1 Cables for Overhead Lines
1. When cables are used for overhead lines, the cables shall be installed not to be inflicted
the tensile strength using messenger wires or other appropriate measures. The messenger
wires shall be installed in accordance with the provision of Clause 41.
2. When cables are installed along a building or another object, the cables shall be supported
not to be damaged by contacting the building or the object.

50.2 Connecting Methods of Overhead Conductors
The tensile strength of the conductors shall not be reduced by 20% or more, when electric
conductors are connected. If the tension working on the conductors is distinctly smaller than
the general tensile strength of conductors this may not apply.

50.3 Branching of Overhead Lines

Branching of overhead lines shall be made at the supporting point of the lines. If branching
shall be done not to inflict tension to conductor at the branch point, this may not be applicable.

Clause 51: Mechanical Strength of Insulators

The insulator to support medium-voltage line shall be installed in such a manner that it has sufficient
strength to attain a safety factor of 2.5 or more based on the assumption that the following loads are
exerted to the insulators..

1. For the insulators to anchor lines, the load is the assumed maximum tension of the lines.
2. For the insulators to support lines, the load is the horizontal lateral load or vertical load exerted
perpendicular to the axis of the insulators.

Clause 52: MV/LV Transformers

MV/LV transformers including medium-voltage conductors other than cables, shall be installed not to be
in danger of electrical shock in either manner of following method.
1. MV/LV transformers shall be installed in an exclusive cabin that is locked.

2. MV/LV transformers shall be installed at the height of 5.0m or more above the ground in order
that persons do not touch them easily.

3. Appropriate fences shall be installed around the MV/LV transformers in order that persons do not
touch them easily and warning signs to indicate the danger are displayed. Otherwise MV/LV
transformers of which charged parts are not exposed shall be installed for persons not to touch
them easily.

Clause 53: Protective Devices

53.1 Installation of Medium-Voltage Over Current Circuit Breakers

1. On a Medium-voltage Lines, an over current circuit breaker shall be installed at the outgoing
point of a substation or similar location and on the primary side of a transformer.

2. Over current breakers for a short circuit protection shall have the ability to break the short circuit
current that pass the breakers.

53.2 Installation of Medium-Voltage Ground Fault Circuit Breakers

A ground fault breaker that breaks circuit automatically when an earth fault happens in the lines shall
be installed at an outgoing point of substation or similar locations.

53.3 Installation of Surge Arresters

To prevent electrical equipment from being damaged by lightning, surge arresters shall be installed
at the places of lines stated below or their surrounding areas. If electric power facilities will not be
damaged by lightning, this may not be applicable.

1. A lead-out of overhead line from power station, substation, and equivalent places.

2. The connecting point of overhead medium-voltage lines with a main transformer.

Clause 54: Height of Overhead Lines

The height of overhead lines shall be no less than the values in the following table;

(Unit: meter)

Low- voltage

Medium-voltage

Urban area

Other area

Cable

Others

Crossing
a road

6.5

8.0

8.0

6.5

Others

5.5

5.5

6.5

5.5

Clause 55: Clearance between Overhead Lines and Other Objects

Minimum clearance between a line and another object shall be the values in the following table;

(Unit: meter)

Low-voltage

Medium- voltage

Structures
of buil dings

Up side
adja -cency

With the
possibility for
persons to
climb on

Bare conductor

–

3.0

Insulated conductor

2.0

2.5

Cable

1.0

1.2

Others

Bare conductor

–

3.0

Insulated conductor

1.2

1.5

Cable

0.4

0.5

Lateral and downside
adjacency

Bare conductor

–

3.0

Insulated conductor

1.2

1.5

Cable

0.4

0.5

Plants

Bare conductor

–

2.0

Insulated conductor

Shall not contact directly

Cable

Shall not contact directly

Low voltage cable including ABC (Ariel Bundle Conductor) type cable may be installed directly on a
wall of a building by isuing clip and clamp in such a way that normally a person cannot reach the cable.

Clause 56:Adjacency and Crossing of Overhead Lines

56.1 Plural Medium-Voltage Lines

When a medium-voltage line is installed adjoining or crossing another medium-voltage line, the
clearance between the two medium-voltage lines shall be 2.0m or more. If one is a cable and the
other is a cable or an insulated conductor, the clearance shall be 0.5m or more.

56.2 Medium-Voltage Lines and Low-Voltage Lines

When a medium-voltage line and a low-voltage line are installed with adjoining or crossing each other,
they shall be installed in the manner of following method.

1. The medium-voltage line shall not be installed under the low-voltage lines. If the medium-voltage
line keeps the horizontal clearance of 3.0m or more with the low-voltage line, and the low-
voltage line does not come in contact with the medium-voltage line when the support structure of
the low-voltage line collapses, this may not be applicable.

2. The clearance between the medium-voltage line and the low-voltage line shall be 0.5m or more
when the medium-voltage line is a cable, 1.0m or more when it is an insulated conductor, and
2.0m or more when it is a bare conductor.

3. The medium-voltage line shall not cross under the low-voltage line. If the medium-voltage line is
a cable and the clearance between the medium-voltage line and the low-voltage line is 0.5m or
more, this may not be applicable.

56.3 Plural Low-Voltage Lines
When a low-voltage line is installed adjoining or crossing other low-voltage lines, the clearance
between the two low-voltage lines shall be 0.6m or more. When one is a cable and the other is a
cable or an insulated conductor, the clearance shall be 0.3m or more.

56.4 Medium-Voltage Lines and Communication Lines

When a medium-voltage line is installed adjoining or crossing a communication line, the medium-voltage
line shall be installed in the manner of following methods.

1. The medium-voltage line shall not be installed under the communication line. If the medium-
voltage line keeps the horizontal clearance of 3.0m or more with the communication line, and the
communication line does not come in contact with the medium-voltage line when the support
structure of the low-voltage line collapses, this may not be applicable.

2. The clearance between the medium-voltage line and the communication line shall be 0.5m or
more when the medium-voltage is a cable, 1.0m or more when it is an insulated conductor, and
2.0m or more when it is a bare conductor.

3. The medium-voltage line shall not cross under the communication line. If the medium-voltage
line is a cable and the clearance between the medium-voltage line and the communication line is
0.5m or more, this may not be applicable.

56.5 Low-Voltage Lines and Communication Lines

When a low-voltage line is installed adjoining or crossing a communication line, the low-voltage line
shall be installed in the manner of following method.

1. The low-voltage line shall not cross under the communication line. If other methods are not
technically realistic, this may not be applicable.

2. The clearance between the low-voltage line and the communication line shall be 0.3m or more
when the low-voltage is a cable, and 0.6m or more when it is insulated conductor.

PART 8

GENERAL REQUIREMENTS FOR HOUSE WIRING

Clause 57: Insulation

The insulation resistance between conductors of low-voltage wiring and between the
electrical circuit and ground shall be no less than the value given in the following table with
respect to the nominal circuit voltage for each section into which the electrical circuit can be
divided by switching devices or over-current circuit breakers.

If insulation resistance measurement is difficult, it is sufficient to keep the leakage current 1 mA
or less.

Clause 59: Protection against Overcurrent
Devices to protect against Overcurrent shall be installed according to Clause 36.

Clause 60: Protection against Ground Fault
On an electrical circuit to supply electricity to low-voltage equipment and devices enclosed
with a metal case and installed at a place where there is the danger of persons easily touching it,
a device shall be installed to interrupt the circuit automatically when a ground fault occurs in the
electrical circuit. However, such a device need not be installed if the situation is under one of the
following:

1. If the equipment and devices are installed in a dry place.
2. If the equipment and devices are covered with rubber, synthetic resin or other insulating
material.
3. In the case of supplying electricity to emergency lighting equipment etc of which could
impair ensured public safety.

Clause 61: Indoor Wiring

61.1 Restriction of bare conductor
Bare conductor shall not be used for indoor wiring.
61.2 Sign of indoor wiring 35
The color sign for neutral conductor shall be black or blue. And the color sign for protective
conductor shall be green or green with white or yellow.

1. No live parts shall be exposed.
The above shall not apply to a place prepared to block out any person other than the operator.
2. The utensil shall be connected fast and electrically safely by screw fastening or the like. In addition, no mechanical tension shall act on the connection point.
3. The indoor wiring shall contain protective grounding conductors beforehand to ensure the grounding of electric equipment.

1. No live parts of electrical household appliances shall be exposed.
2. No live parts of low-voltage business electrical appliances shall be exposed. However the above shall not apply to appliances that are used with some live part inevitably exposed and the case that these are installed in a place made inaccessible for any person other than the operator.
3. If the indoor electric appliance is connected to an electrical conductor, the electrical conductor shall be connected fast and electrically perfect. In addition, no mechanical tension shall act on the connection point.

Clause 64: Indoor Wiring for Adjacency and Crossing

The low-voltage indoor wiring shall be installed in such a manner so as not to contact a telecommunication conductor, water supply pipe, gas pipe or other similar object.

Clause 65: Outdoor Installation at user’s site

65.1 Overhead low-voltage service drop lines

1. Height from ground
The height from the ground surface shall be not less than 4 m, and no less than 6.5 m for road crossing.
2. Clearance to other objects
A low-voltage overhead service drop line shall be installed according to Clause 55. For a building in which a low-voltage overhead service drop line is directly installed, or if it is technically difficult to install such facilities according Clause 55, A low-voltage overhead service drop line shall be installed in such a manner that a person cannot reach it even if he or she stretches out his/her hand from a window, corridor, or a passage where person can ordinarily access.

65.2 Other outdoor Installation at user’s site The wire or cable shall be in a conduit if people have possibility of touching them.
Outlets shall be waterproof type if they have possibility of taking rainwater.
A protective device shall be installed if it is considered danger.

No less than the value by adding 0.06 m for every
10kV over 35kV to 3m;